The invention relates to a method for operating an internal combustion engine, especially in a motor vehicle.
To enable efficient operation of internal combustion engines with as little pollution as possible, especially in motor vehicles, their control sophistication is being continuously increased. Thus, among other things, ignition control and fuel metering are becoming more and more complicated and the induction systems are being improved. It is known by DE-A-35 29 388, for example, that to achieve good filling of the combustion chambers over the rpm range of the internal combustion engine, an induction manifold can be provided, in which--in the lower rpm and load range--long induction pipes (tuned induction pressure charging [resonance mode]) and--in the upper rpm range--short induction pipes take effect with an increased induction volume. Switching over in the form of throttle valves generally takes place depending on rpm and/or depending on induction pipe pressure. However, it is of decisive importance that these measures for improving the power and efficiency with favorable pollutant values interact without problems.
In addition, by virtue of DE-A-39 04 412, an induction system is known with an air flow rate and--associated with it--fuel metering, on the one hand, which are controlled via a main throttle valve, and in the idle range are controlled via a bypass system which bypasses the main throttle valve. There is a memory which stores a numerous reference values of the pressure in the induction area which are derived in agreement with the engine rpm and the degree of opening of the throttle valve. Furthermore, there is a pressure transducer for sampling the pressure in the induction port, and an engine rpm sensor. A throttle valve position transducer samples the degree of opening of the throttle valve; another position transducer determines the degree of opening of the valve in the bypass. To monitor the systems, there are comparator means which compare the pressure value measured by the pressure transducer to a reference pressure derived from the memory and which deliver an error signal when the sampled pressure does not match the computed reference pressure. The error signal can thus lead, for example, to cutoff of fuel feed.